Hierarchically Porous Carbons Derived from Cotton Stalks for High‐Performance Supercapacitors

Abstract In this work, cotton stalks (CSs), as an earth‐abundant biomass, were originally proposed as a new carbonaceous precursor to prepare hierarchically porous carbons (HPCs) with the activation of various concentrations of H 3 PO 4 at high temperatures. A variety of measurements including SEM, TEM, N 2 adsorption/desorption analysis, XPS and FTIR have been adopted to systemically investigate the micromorphology, pore structure, and surface chemistry of the HPCs. The CS‐derived HPCs (CSHPCs) have large specific surface areas up to 1403.123 m 2 g −1 and a broad pore‐size distribution indicates their hierarchically porous structures. Furthermore, electrochemical measurements including electrochemical impedance spectroscopy, galvanostatic charge/discharge and cyclic voltammetry were used to evaluate the capacitance and rate performance of the HPCs. The investigations illustrated that CSHPCs possess a high specific capacitance up to 175 F g −1 at a scan rate of 5 mV s −1 in 2 M KOH. In addition, CSHPCs have good long‐term cycling stability and more than 90 % of the initial capacity is retained after 10000 cycles at a large current density of 1 A g −1 .